PHYSIOLOGICAL. 

 CHAEYBDEA. 



Light and Darkness Experiments 1-9, 10, 33, 34. As already stated 

 in the Introduction, a part of Conant's experiments were performed 

 in a photographer's dark-room, with the animals in a deep glass jar. 

 In the dark a fair proportion of the animals became nearly quiescent 

 on the bottom, but upon lighting a lamp many started up immediately, 

 while others took a longer time to come to the surface and swim. 

 These experiments were tried a number of times and on different 

 occasions with very similar results. Some medusa?, however, tried 

 immediately after being brought in, seemed not to react so well upon 

 being placed in the dark-room, nor would they become quiescent. 

 This, probably, was due to the fact that the animals had not yet 

 recovered from the effects of being caught and placed in new 

 surroundings. (Experiments 1, 2, 3.) 



Other experiments (4-8, 33, 34) were tried by carrying the jar 

 with the animals from the weaker light of a room into the more 

 intense light of outdoors or into direct sunlight. The usual result 

 was an inhibition of pulsation and a settling to the bottom, while 

 the medusaB immediately became active again upon returning with 

 them to the room. These results were so marked that no doubts can 

 be entertained as to their cause, though some exceptions occurred in 

 which animals placed in the sun continued to swim on the surface 

 or soon recovered pulsation. In some experiments, too, no animals 

 responded to the inhibitory stimulus of the brighter light or all very 

 soon recovered. (See, however, Temperature. )_ 



Reducing the light by placing a coat over the jar produced 

 the same effect in some experiments (8, 9, 10) as did reducing the 

 light in other ways, while removing the coat produced the same 

 effect as exposure to brighter light. In these instances it appears 

 to be the transition from weaker to stronger light that inhibits 

 pulsation, rather than the actual intensity of the light ; and vice versa. 

 It must be noted, too, that when left for some time in any one place 



